The 3rd Generation Partnership Project (3GPP) standardization develops a brand new evolved network, and system architecture evolution (SAE) of the evolved network is shown in FIG. 1. In SAE architecture, after a user equipment (UE) accesses an evolved universal terrestrial radio access network (E-UTRAN) through a radio air interface, the UE first attaches to a mobility management entity (MME). The MME acquires user subscription data and authentication information from a home subscriber server (HSS), and initiates a process of performing authentication on the UE. After the MME completes the authentication process, the UE or the MME initiates a process of establishing a bearer used for transmitting user data. In the process, the MME notifies a serving gateway (S-GW) to establish, for a user, a bearer that is from the E-UTRAN to a packet data network gateway (P-GW) and is used for transmitting user data, where a notification message carries an address of the P-GW and address information of an E-UTRAN network element where the user resides. The P-GW forwards downlink data from an external packet data network (PDN) to the UE through the bearer, and forwards uplink data from the UE to a corresponding PDN.
To be compatible with the existing universal terrestrial radio access network (UTRAN) and global system for mobile communications/enhanced data rates for GSM evolution radio access network (GSM/EDGE radio access network) (GERAN), the UE may access the MME through the UTRAN or GERAN and a serving general packet radio service (GPRS) support node (SGSN), and may establish a GPRS tunnel protocol (GTP) tunnel connection with the S-GW through the UTRAN/GERAN and the SGSN. The S-GW converts a GTP tunnel into a corresponding bearer that connects to the P-GW and is used for transmitting user data. The UTRAN may also establish a GTP tunnel that directly connects to the S-GW. The MME serves as a network element that processes only control plane signaling, and the S-GW and the P-GW are mainly responsible for forwarding user plane data. The S-GW and the P-GW may be combined into one network element, and may be referred to as a unified gateway (UGW).
With the development of mobile Internet services, enrichment of enterprise network services, and integration of mobile access networks of multiple RATs, a gateway device needs to be gradually developed toward more refined service control and charging based on implementation of a basic data forwarding function, so as to support more abundant service implementation and control demands from an operator. Meanwhile, in an evolved network, a UGW still needs to maintain a large number of external signaling interfaces. These signaling interfaces include a GTP control plane (GTP-C) bearer interface between an MME and a gateway, a policy and charging control (PCC) interface between a policy and charging rules function (PCRF) and the gateway, a charging interface between a charging system and the gateway, a lawful interception interface between a lawful interception device and the gateway, a dynamic host configuration protocol (DHCP) interface between a DHCP server and the gateway, an interface between an authentication, authorization and accounting (AAA) server and the gateway, and the like.
In order to process a large amount of interface signaling, a large amount of hardware such as a general computing processor chip is added to the gateway on the basis of a dedicated hardware platform, so that a hardware platform of the gateway device is quite complex and has an excessively high cost, which is adverse to the promotion and deployment of mobile packet data networks.
To solve the foregoing problem, a scenario where a control plane and a forwarding plane of the gateway are separated emerges currently, that is, the gateway is divided according to functions into a gateway control plane (GW-C) and a gateway forwarding plane (GW-U), and an interface between the GW-C and the GW-U is defined as Sg. In a charging process, the GW-C implements user access, policy control and charging bill management and the GW-U is mainly responsible for forwarding data and executing control and a first charging policy delivered by the control plane. However, when a communication failure occurs to the Sg interface, the GW-U cannot send collected charging information through the Sg interface to the GW-C to generate a charging bill, thereby causing that the charging information is lost.